Your functions are backwards...

[dafyddcrosby]

Your functions are backwards...

[dafyddcrosby]

@abferm First, thanks for taking a look! I'd forgotten about this module :-)

These functions implement 'natural' binary-coded decimal: http://en.wikipedia.org/wiki/Binary-coded_decimal#Basics

So the functions handle the encoding/decoding per-nibble, and the BCD should be treated as a string (not obvious from the source - I hadn't really expected reuse of this module ;-) and you need to take a look at the binary to see what's going on.

So for the doctest:

>>> int_to_bcd(34)
22

The integer

00100010
87654321
bit 2 and bit 6 are 1, which is 2 + 32 = 34

Broken down into nibbles for BCD

0010 0010
Which, referencing the table in Wikipedia, 0020 is 2. "2" + "2" = "22"

When you see the BCD as a string, int 34 -> bcd "22". I'll add some documentation so that this behaviour is a little more obvious. Again, thanks for taking a look!

[abferm]

I think I was misinterpreting what your methods were trying to do. From my understanding int_to_bcd would return the bcd equivalent of the provided integer, not decode an integer as BCD. In other words I expected int_to_bcd(22) to return binary 0010 0010 which is integer 34.

----- Original Message -----
From: "David T. Crosby" [email protected]
Date: Sunday, May 31, 2015 10:17 am
Subject: Re: [python-bcd] Your functions are backwards... (#1)
To: dafyddcrosby/python-bcd [email protected]
Cc: abferm [email protected]

@abferm First, thanks for taking a look! I'd forgotten about this module :-)

These functions implement 'natural' binary-coded decimal: http://en.wikipedia.org/wiki/Binary-coded_decimal#Basics

So the functions handle the encoding/decoding per-nibble, and the BCD should be treated as a string (not obvious from the source - I hadn't really expected reuse of this module ;-) and you need to take a look at the binary to see what's going on.

So for the doctest:

int_to_bcd(34) > 22 >
The integer
00100010 > 87654321 > bit 2 and bit 6 are 1, which is 2 + 32 = 34 >
Broken down into nibbles for BCD
0010 0010 > Which, referencing the table in Wikipedia, 0020 is 2. "2" + "2" = "22" >
When you see the BCD as a string, int 34 -> bcd "22". I'll add some documentation so that this behaviour is a little more obvious. Again, thanks for taking a look!
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[dafyddcrosby]

Ah, that makes sense. How do additional int_to_binary_bcd and binary_bcd_to_int functions sound? Clearer input/outputs, I think...

[abferm]

Possibly, I'm surprised that yours is the only BCD library I could find without a whole lot of searching. Would you consider adding an init.py file to make it a true module?

----- Original Message -----
From: "David T. Crosby" [email protected]
Date: Monday, June 1, 2015 11:25 am
Subject: Re: [python-bcd] Your functions are backwards... (#1)
To: dafyddcrosby/python-bcd [email protected]
Cc: abferm [email protected]

Ah, that makes sense. How do additional int_to_binary_bcd and binary_bcd_to_int functions sound? Clearer input/outputs, I think...
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